Short-range order in Au-Fe alloys studied by high-temperature Mössbauer spectroscopy

Local atomic configurations of iron atoms in ${\mathrm{Au}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Fe}}_{\mathrm{x}}$ alloys with x=0.01,0.05,0.15 are investigated from 300 up to 1100 K using high-temperature Mössbauer spectroscopy. In all alloys a short-range order (anticlustering) tendency is observed. Complementary x-ray small-angle scattering experiments reveal no Fe clusters of the Guinier-Preston-zone type in agreement with the result from Mössbauer experiments. The temperature dependence of the first short-range-order parameter, ${\alpha }_1$, obtained from the Mössbauer spectra, is surprisingly weak. A computer simulation shows that, however, the short-range-order can be temperature dependent due to the effect of higher-order correlations, namely third-neighbor Fe-Fe pairs. These higher-order correlations may play an important role for the magnetic properties at low temperature.